Superchargers are air pumps or blowers in the intake system of an internal combustion engine for increasing the mass flow rate of air charge and consequent power output from a given engine size. Turbosuperchargers (normally called turbochargers) are engine exhaust gas turbine driven superchargers. When superchargers are driven mechanically from the shaft of the internal combustion engine, a speed increasing gear box or belt drive is needed. Such superchargers are limited to a relatively low rotating speed and are large in size. Paxon Blowers and Vortech Engineering Co. are marketing such superchargers. Fixed gear ratio superchargers suffer from two very undesirable features: 1) there is a sharp decrease in boost pressure at low engine RPM because boost pressure goes generally to the square of the speed of rotation, and 2) it is generally difficult to disconnect the supercharger from the engine when the supercharger is not needed.
Applicant was granted on Dec. 5, 1995 a patent (U.S. Pat. No. 5,471,965) on a very high speed radial inflow hydraulic turbine. FIG. 12 of that patent discloses the hydraulic turbine driven blower used in combination with a conventional turbocharger to supercharge an internal combustion engine. In that embodiment the output of the hydraulic driven compressor was input to the compressor of the conventional turbocharger. In all the embodiments shown in the '965 patent, the pump delivering high pressure hydraulic fluid to the hydraulic turbine was driven directly off the engine shaft. At high speeds when the exhaust driven turbosupercharger is fully capable of supplying sufficient compressed air to the engine, a bypass valve unloaded the hydraulic fluid pump but it continued to pump hydraulic fluid through the bypass valve which is a waste of engine horse power.
Another hybrid supercharger is disclosed in U.S. Pat. No. 4,285,200 issued to Byrne on Aug. 25, 1981. That patent disclosed a compressor driven by an exhaust driven turbine and a hydraulic driven turbine, the compressor and both turbines being on the same shaft. That turbine was an axial flow turbine and the turbine was driven with engine oil. With this design oil foaming can be a problem. U.S. Pat. No. 5,471,965 and U.S. Pat. No. 4,285,200 are incorporated herein by reference.
Many motor vehicles being produced at the time of the filing of this application utilize high pressure fluid to drive devices such as power steering equipment. These devices typically are designed for higher pressure hydraulic fluid than the preferred hydraulic fluid pressures needed for hydraulic fluid driven superchargers.
There is a great need for additional supercharging of present turbocharged diesel engines. In the low RPM range, the currently available turbocharging systems are not very effective in producing sufficient engine manifold pressure and power, required for satisfactory vehicle acceleration and exhaust smoke reduction. This applies especially to "stop and go" type services, such as city buses and trash collecting trucks. A thermodynamic cycle analysis of a typical truck turbodiesel engine shows that even with modest 2 to 3 psi supercharging applied in series to the inlet of the existing turbocharger compressor in the low engine RPM range, the existing turbocharger pressure ratio increases exponentially mainly due to a large increase in turbocharger turbine power.
What is needed, is a better supercharger system.